Differential Diagnosis for Recurrent Uric Acid Stones in a 16-Year-Old Girl

Single Most Likely Diagnosis

• Insulin Resistance Syndrome: This condition is closely associated with obesity, which is a significant risk factor for uric acid stone formation. Insulin resistance can lead to increased uric acid production and decreased urine pH, both of which are conducive to uric acid stone formation. The patient's elevated urinary uric acid level and low urine pH support this diagnosis.

Other Likely Diagnoses

• Dietary Factors: A diet high in animal protein, sodium, and sugar can increase the risk of uric acid stone formation by increasing uric acid production, reducing urine pH, and increasing urinary sodium excretion. The patient's elevated urinary sodium level suggests a high-sodium diet.
• Low Urine Volume: Although the patient's 24-hour urine volume is 2.1 L, which is within the normal range, it may not be sufficient to prevent stone formation, especially in the context of other risk factors.
• Gout: Although less common in adolescents, gout can cause uric acid stone formation. However, the absence of other symptoms such as joint pain and the patient's age make this diagnosis less likely.

Do Not Miss Diagnoses

• Type 2 Diabetes Mellitus: This condition can cause urinary tract infections, increase the risk of stone formation, and is associated with insulin resistance. Although the patient's symptoms do not directly suggest diabetes, it is essential to rule out this condition due to its potential severity and the patient's obesity.
• Primary Hyperparathyroidism: This rare condition can cause hypercalciuria, which may contribute to stone formation. Although the patient's calcium level is within normal limits, primary hyperparathyroidism can also cause other symptoms such as bone pain and kidney damage.

Rare Diagnoses

• Lesch-Nyhan Syndrome: This rare genetic disorder is characterized by excessive uric acid production, which can lead to stone formation. However, the patient's age, sex, and lack of other symptoms such as intellectual disability and self-mutilation make this diagnosis unlikely.
• Tumor Lysis Syndrome: This condition can cause excessive uric acid production, but it is typically associated with cancer treatment and is unlikely in this patient without a history of cancer or chemotherapy.